The present invention relates to apparatus for forming holes in poured concrete walls and, in particular, to a discontinuous band assembly which mounts between opposite, facing form walls to define a void or through hole in the poured walls of the formed concrete.
The formation of holes in poured concrete structures can be achieved with a variety of available molding or forming dies or mandrels. These dies can range from rudimentary to complex assemblies.
The size and shape of a desired aperture can affect the pouring process and the ability of a fabricator to cost effectively form a desired number of holes of desired sizes and shapes. That is, where multiple holes are required at sizes in excess of twelve inches, it frequently becomes necessary to use commercially available forming die sets which are rather costly to obtain and inventory for most fabricators. Correspondingly, one die set is required for each desired hole. For many monolithically cast structures, a large number of die sets can be required. The casting forms must also be compatible with the hole forming dies; thus the cost to pour a desired structure is affected by forms availability.
For small production runs or small hole sizes, rudimentary dies may consist of a solid or hollow object having a shape corresponding to the desired hole, such as a length of pipe or a solid pre-formed plug which is capable of being mounted between the walls of the casting mold. While a variety of plugs exist for planar wall structures, curvilinear walls present many difficulties that are not readily overcome without the benefit of specially prepare assemblies.
Various assemblies for forming relatively small diameter gasketed holes in poured concrete structures can be found upon referencing to U.S. Pat. Nos. 3,727,876; 3,832,438; 4,625,976; 4,805,920; 4,842,785; and 4,951,914. The hole forming assemblies of the foregoing references each generally provide mandrels which are supported to the casting form walls with through fasteners that bolt to the form walls.
Each form supports an elastomer gasket which is cast in place at the structure wall. The forms are constructed as unitary or multi-part assemblies. The latter assemblies, which are disclosed at the 4,842,785; 3,832,438; 3,727,876; and 4,625,976 patents, provide fixed diameter annular assemblies which are compressively drawn into engagement with each other and the gasket. The gasket is thus pinched to the casting form.
U.S. Pat. No. 5,171,507 discloses another fixed sized casting mandrel which is manufactured by Del Zotto Manufacturing, Inc., the assignee of the subject invention.
U.S. Pat. No. 4,801,417 discloses a manhole casting form which supports multi-section hole formers from holes cut into a wire meshwork, prior to forming. Although the hole former molds are distinguishable from the present assemblies, an inner wall form of the manhole casting mold assembly provides a large diameter band having mating edges which are restrained together via a hinge assembly. The hinge assembly permits relaxation of and expansion of the form after the form is stripped from the cast structure. In contrast to the present invention, the form expands outward. Preferably, the form should collapse inward to facilitate release from the cast structure.
In appreciation of the foregoing deficiencies, the present invention provides a variety of hole former assemblies. The assemblies are readily constructed from flat metal stock and can be formed to accommodate planar or curvilinear pouring forms. The assemblies are constructed to be passively retained between assembled, molding forms. The walls of each assembly collapse inward to facilitate release from a poured structure.